An argument has broken out over the authenticity and significance of an ancient text that makes explicit reference to Jesus having a wife.

Karen King, a professor and expert in the history of Christianity at Harvard Divinity School, revealed a fourth-century fragment of papyrus with dialogue, in which, she said, researchers had identified the words "Jesus said to them, 'my wife'", which may refer to Mary Magdalen.

The discovery, which could spark debate over celibacy and the role of women in Christianity, was unveiled by King on Tuesday at an international congress on Coptic studies in Rome.

Christian tradition holds that Jesus did not marry. But a number of experts vouched for the authenticity of the fragment. They said, in the early years, Jesus's marital status was subject to debate. This text, they added, proved that some early Christians believed Jesus was married.

But Wolf-Peter Funk, a professor and noted Coptic linguist, who co-directed the francophone project editing the Nag Hammadi Coptic library at Laval University, in Quebec, questioned the claim. He said there were "thousands of scraps of papyrus where you find crazy things", and many questions remained unanswered about the Harvard fragment.

Jim West, a professor and Baptist pastor in Tennessee, was also sceptical: "A statement on a papyrus fragment isn't proof of anything. It's nothing more than a statement in thin air, without substantial context."

Ben Witherington III, a biblical scholar and professor at Asbury theological seminary, in Wilmore, Kentucky, added that the unclear origins of the document should encourage people to be cautious. "The document follows the pattern of gnostic texts during the strong monastic periods of the second, third and fourth centuries, [in which] the language of intimacy [was used] to talk about spiritual relationships.

"What we hear from the gnostic is this practice called the sister-wife texts, where they carry around a female believer who cooks for them and cleans for them and does the usual domestic chores, but [with whom] they have no sexual relationship whatsoever.

"In other words, this is no confirmation of … the idea that the gnostics thought Jesus was married in the normal sense of the word."

King said the fragment was a copy of a gospel, probably written in Greek in the second century. She said the four words in the 3.8cm x 7.6cm fragment were written in Coptic script, a language of ancient Egyptian Christians. "The words translate as 'Jesus said to them, my wife'. The fragment also includes dialogue between Jesus's disciples, during which they discuss whether Mary is worthy, and Jesus replies 'she can be my disciple'."

King emphasised that the fragment did not prove Jesus was married. Instead, she said, it spoke "to issues of family and marriage that faced Christians".

Christian tradition has long held that Jesus was unmarried even though there has been no reliable historical evidence to support that stance, King said. The new gospel "tells us that the whole question only came up as part of vociferous debates about sexuality and marriage".

"From the very beginning, Christians disagreed about whether it was better not to marry. But it was over a century after Jesus's death before they began appealing to Jesus's marital status to support their positions."

King presented the document at a six-day conference at Rome's La Sapienza University and at the Augustinianum institute of the Pontifical Lateran University.

Although the Vatican newspaper and Vatican Radio frequently cover academic conferences, there was no mention of King's discovery in any Vatican media on Tuesday.

The fragment belongs to an anonymous private collector who contacted King to help translate and analyse it. Nothing is known about the circumstances of its discovery but King said it came from Egypt. t was written in a script used there in ancient times. King acknowledged there were doubts about the authenticity of the papyrus fragment. But, she said, they should not stop scholars from continuing to examine it.

Those who did an initial examination of the fragment include Roger Bagnall, a papyrologist, who is director of the New York-based Institute for the Study of the Ancient World, and AnneMarie Luijendijk, a scholar of the New Testament and early Christianity from Princeton University.

They said their study of the papyrus, the handwriting and how the ink was chemically absorbed, showed it was "highly probable an ancient text", King said.

Another scholar, Ariel Shisha-Halevy, a professor of linguistics at the Hebrew University, Jerusalem, and a leading expert in Coptic language, reviewed the text's language and concluded it "offered no evidence of forgery".

King and Luijendijk said they believed the fragment was part of a newly discovered gospel. They have named it the "Gospel of Jesus's Wife".

King said she dated the time it was written to the second half of the second century because the fragment showed close connections to other newly discovered gospels written at that time, especially the Gospel of Thomas, the Gospel of Mary and the Gospel of Philip.